Manufacturers of compression-ignition engines face increasingly stringent emissions standards in the future, including reductions in allowable levels of nitrides of oxygen (‘NOx’) and particulate matter (‘PM’). Broadly speaking, reducing emissions is achieved by reducing engine-out emissions, or by converting engine-out emissions to harmless gases using some form of exhaust gas aftertreatment, including converters, traps, or afterburners. Systems and methods to reduce engine-out emissions can include systems which premix fuel and air before entrance to the combustion chamber.
Achieving low emissions levels is especially challenging at high-load engine operating conditions. Known fuel/air pre-mixing concepts are able to achieve low NOx and PM emissions at low engine load levels. However, such systems are often not operable during higher engine load operation due to excessive combustion noise, among other problems.
Therefore, there is a need for improved operation of a compression-ignition engine to address the aforementioned concerns.